Die singulation refers to the step or steps used to separate individual die sites from the semiconductor wafer and to form discrete semiconductor dies. A variety of different techniques can be used to cut the semiconductor wafer in a singulation process. Examples of these techniques include mechanical sawing, laser cutting and chemical etching techniques, to name a few. These techniques suffer from various drawbacks including the formation of cracks in the active area of the semiconductor dies and/or the formation of recast material on the main surface of the semiconductor wafer. These drawbacks can detrimentally impact yield and/or performance of the discrete semiconductor dies.
One technique that is used to improve known die singulation processes is the inclusion of a so-called kerf clean processes. This process is used to remove structures, such as test structures and/or lithography alignment features, that are formed in the kerf regions of the semiconductor wafer prior to singulation. This prevents the kerf region structures from interfering with the cutting mechanism (e.g., a saw blade). However, known kerf clean processes add substantial cost to the process, and result in rough surfaces which are susceptible to cracks and/or reduction in die strength.
Silicon Carbide (SiC) technology presents unique challenges with respect to die singulation. Due to the hardness of the SiC material, mechanical sawing techniques commonly cause chipping of the material, resulting in yield losses. Moreover, the hardness of the SiC material causes wear and breakage of saw blades. For this reason, a laser ablation is commonly used to cut SiC or SiC based wafers. One drawback of laser ablation is that, the vapourized semiconductor material can reform on the main surface of the semiconductor dies as recast material, which can lead to yield losses and complete device failure.